GB1069754A - Improvements in apparatus for x-ray analysis of a material - Google Patents

Abstract

1,069,754. Photo-electric X-ray analysis. J. BAECKLUND. June 3, 1964 [June 7, 1963], No. 23010/64. Heading G1A. [Also in Division H5] In apparatus for the analysis of a specimen by X-rays, a filter 2 (Fig. 1) is interposed between the X-ray tube 1 and the specimen 3, the filter having a high absorptivity within a range of wavelengths containing a definite wavelength to be considered, and a low absorptivity at shorter wavelengths. When the specimen is to be analyzed to determine the concentration of a particular constituent element, some of the primary radiation from the X-ray tube anode is scattered from the sample and forms a background specimen on which the characteristic fluorescent radiation of the sample is superimposed. If the particular wavelength of the constituent to be considered coincides with the characteristic lines of the X-ray source, the accuracy of the measurements will be affected. To counteract this, instead of replacing the X-ray tube by one with a different anode material, a filter of an element dependent on the anode material, is interposed as stated above. For example, in the analysis of a steel specimen, for the determination of the chromium content, when a chromium anode is used, the background radiation Fig. 2 (not shown) has a peak at the wavelength which is to be used in the measurement of the chromium content. The interposition of a titanium filter (having an absorption characteristic as in Fig. 3, not shown) reduces the unwanted line to reasonable proportions Fig. 4 (not shown). The shorter wavelength primary radiation which produces the fluorescent radiation of the specimen, is passed by the filter with little attenuation. In the determination of lead, tantalum or bismuth in steel, a tin filter is necessary. The apparatus is designed so that the filter for the determination of a particular constituent can be switched in when needed. This is decided by the angular displacement of the detector 6 with respect to the diffraction crystal 5. A number of filters are therefore carried in a special mount Fig. 7 (not shown) attached to a permanent magnet and coil arrangement, operated by signals from a switching unit controlled by the actuation mechanism which displaces the detector 6.